This invention relates to a photographing apparatus for an endoscope, which is used for automatic exposure signal circuits, and in which the coupling between a camera and the endoscope and/or coupling between the endoscope and a light source unit are free from mechanical electric switches or contacts.
In the usual photographing apparatus for an endoscope, a camera and a light source for the endoscope are electrically coupled together. This coupling is made for the purposes of synchronizing flashlight for photographing and shutter release action and obtaining automatic exposure control. Usually, the coupling is accomplished through a plurality of mechanical electric switches or contacts provided in a connector section on the side of an eyepiece section of the endoscope. These switches or contacts are all exposed on the outer surface of the connector section, so that contact failure is likely to result from such causes as their contamination, oxidation and corrosion. This drawback can be avoided by adopting a water-proof construction for the switches. However, water-proof electric switches are complicated in construction and cannot fundamentally solve the problem.
There are teachings concerning the solution of the above problem, for instance one disclosed in Japanese Patent Disclosure No. 38322/78. In this disclosure, a light emission device is provided in the camera, and a light reception device is provided in the light source section. Light emitted from the light emission device is transmitted through a signal light guide within the endoscope to the light reception device. The disclosed apparatus makes use of light emitted from the light emission device as a synchronizing signal for the flashlight. Thus, no mechanical electric switches for the synchronization purposes are needed. However, this apparatus cannot be adopted where the automatic exposure control is made on the light source side.